I'm working on a HTML5 Canvas whiteboard.

I store all my elements on the stage in an array.

Now I added a drawing function. I can draw and select the drawn object. Now I want to resize the object.

My Paint Class

class Paint {
    constructor(
        id="", coordinates =[], color = '', type="paint", x=0, y=0, width=0, height=0
    ) {
        this.id = id;
        this.coordinates = coordinates,
        this.fillColor = color;
        this.type = type;
        this.x = x;
        this.y = y;
        this.width = width;
        this.height = height;
        
    }

    update() {
        let { coordinates, color,x,y,width,height} = this;
        ctx.save();
        let xx;
        let yy;
      
        
        coordinates.map((dot,index) =>{

            if(index == 0)
            {
                x = dot.startX;
                y = dot.startY;
                xx = dot.mouseX;
                yy = dot.mouseY;
            }

            if(dot.startX < x)
            {
                x=dot.startX; 
            }
            if(dot.startY < y)
            {
                y=dot.startY; 
            }
            if(dot.mouseX>xx)
            {
                xx=dot.mouseX;
            }
            if(dot.mouseY>yy)
            {
                yy=dot.mouseY;
            }

            let startX =  (dot.startX - dx);
            let startY =  (dot.startY - dy);
            let mouseX =  (dot.mouseX - dx);
            let mouseY =  (dot.mouseY - dy);

            ctx.beginPath();
            ctx.lineWidth = 5;
            ctx.lineCap = 'round';
            ctx.strokeStyle = '#ACD3ED';
            ctx.moveTo(startX, startY);
            ctx.lineTo(mouseX, mouseY);
            ctx.stroke();

        });
        this.x = x;
        this.y = y;
        this.width = xx-x;
        this.height = yy-y;
    
        ctx.restore();
    }
}

A result could look like this:

Positions are stored in this format:

If want to resize the drawing proportional if I drag a corner of the calculated rectangle.

I hope someone can help me with that problem.

thanks in advance Frank